Starting battery

[Coppifan]

I'd like to add a starter battery to my boat. I currently have two wet cells in tandem for everything. Had to get a jumpstart from BoatUS towboat today getting back into the river. I let the chiller unit run all night as I was on shore power. I believe something went wrong and the batteries must have taken over...

I have hull #270' 1980.. How do begin? Where should I put it? I have an antique battery selector, the old round red ones. My battery charger does have the wires to allow a third battery. Any and all suggestions are appreciated. Please use small words, I don't know a darn thing about electronics  .. Thanks.
Bill Eggert
West river, Maryland

[Captain Bri]

My P323 had 3 banks of exhausted batteries which I have replaced and converted back to the original two bank system. In my opinion the third bank just seemed to complicate things, and is difficult to set up properly for efficient use and recharge. The original battery box of about 15"x16" will accommodate a pair of Group 24 or Group 27 batteries (my two Trojan T105's as a house bank). A small plywood shelf has been added for the starter battery just outboard and braced against the original box. Each battery is enclosed in a covered plastic box and strapped down (boxes about $8 at Walmart). 

Instead of relying on human intervention (and memory) to change the selector switch between banks, I chose to manage them (deep cycle + starter) using Blue Sea's "Add a Battery" system -- a rotary switch and a relay which electrically isolates the starter battery to preserve its charge, but insures that both banks get charged by use of an Automatic Charging Relay (ACR). The rotary switch only needs to be switched ON when arriving at the boat and it includes a "combine" position as an emergency jump-start feature if your starter battery should fail to crank.

The Blue Sea Website provides good technical information for DIY.  It is similar to a combiner system I have seen from Ample Power (less of a DIY) which is well respected in the industry.  I bought wet cell golf cart batteries locally, and parts from Defender.com (no sales tax), such as marine grade wire from Camco at a fraction of the high price of Ancor wire at WestMarine. I am using the system in production and will report back.

[Dolce_Vita]

I did this last year on Dolce Vita.

We originally had two equal house banks of group 31D batteries
at 97 amp-hours each.  I paralleled them into one big house bank,
and added a smaller, dedicated starter battery as the other bank.

At the dock, charging is provided by my Xantex charger, which has
multiple charging outputs. Although it can handle three banks, I
only needed it to do two because the paralleled batteries look like a
single batery to the charger.  Since the charger can only do one type
of battery, I had to use a gel-cell for my starter, same as the
house batteries.

Under way, charging is provided by the alternator to whatever bank
is selected.  Normally, I always use the house bank for everything,
even starting.  The dedicated starter battery is strictly a backup
in case we drain the house bank.

This arrangement has worked pretty well, but I plan to add a charge
combiner that will automatically charge both batteries regardless of
the position of the battery bank switch.  It's made by
Hellroaraing Technologies:  http://www.hellroaring.com/marine.php

Hope this helps.  Nigel Caulder's book is really the definitive
treatment on marine electrical systems:

Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems

You should get a copy.  Its available at Amazon.

[AnaMeg]

I have a set up similar to Dolce Vita. I use a Xantrex echo charger to charge both batteries from the alternator, a Xantrex charger on shore power with 3 battery capability. I don't recall what the echo charger cost, I think around $120. My master switch is a Blue Seas panel with separate switches for house and starter battery and an "emergency" cross over for use if the starter battery is dead.

My battery "box" was similar to Sea Fever's. I tore it out and made a box under the aft starboard settee that holds 2 4D AGM batteries. One problem is the weight of the house batteries is enough to cause a 2 degree list to starboard. The fit is near perfect. I removed the alcohol container and made a box for a Optima starter battery there.  AGM and gell batteries can be mounted in any position except upside down. The starter battery fits nicely in the space between the nav seat and the engine cowling when setting on end, posts forward for access.

Geoff

[Now or Never!]

Now or Never! has two banks--a start bank and a house bank, all group 27s.  I almost never use the battery selector switch.  the banks are connected via a combiner that combines both banks when receiving a charge and isolates them when discharging.  $85 well spent.  I got the combiner from Yandina Electronics. 
http://yandina.com/c100InfoR3.htm
It has worked flawlessly for at least 5 years.

Peter
Now or Never! Hull 125

[nickzchef]

I added a starting battery (now have three batteries) directly to the left of the two house batteries, used pressure treated wood to make a frame and liquid nails to secure. Had to cut/miter the pressure treated to match the curve of the hull.  Then added another battery switch directly below the other one. 18 years no problems